Insoluble Polyimide Research Articles

Coaxial electrospun nanofibrous substrates with tunable wettability for constructing cucurbit[n]uril-embedded organic solvent nanofiltration membranes

Solvent resistance and high perm-selectivity have always been the pursuit in organic solvent nanofiltration field. Insoluble polyimide nanofibrous membranes feature superior solvent resistance. However, its high hydrophobicity usually limits the uniform spread of the aqueous amine monomers during the interfacial polymerization process, resulting in the non-uniform reaction with the acyl chloride and the defective selective layer. Herein, coaxial electrospinning was employed to construct the core–shell nanofibrous substrates, in which aminated multi-walled carbon nanotubes were added to the shell layer. This strategy endowed the nanofibrous substrates with tunable wettability without sacrificing stability, which guaranteed the one-step construction of defect-free thin-film nanofibrous composite membranes via interfacial polymerization (IP). Further, cucurbit[6]uril was embedded into the polyamide network by coupling host–guest chemistry and IP, providing the wider solvent transport channels and achieving the four times enhanced methanol permeance (22.34 L·m−2·h−1·bar−1) without sacrificing the selectivity. The membrane shows application prospects for solvent recovery in chemical, pharmaceutical, and other fields. This work provides new thoughts for the design and modification of novel nanofiltration membranes.

Selective Destruction of Soluble Polyurethaneimide as Novel Approach for Fabrication of Insoluble Polyimide Films.

Polymeric coatings and membranes with extended stability toward a wide range of organic solvents are practical for application in harsh environments; on the other hand, such stability makes their processing quite difficult. In this work, we propose a novel method for the fabrication of films based on non-soluble polymers. The film is made from the solution of block copolymer containing both soluble and insoluble blocks followed by selective decomposition of soluble blocks. To prove this concept, we synthesized copolymer [(imide)n-(polyurethane)]m, in which the imide blocks were combined with polyurethane blocks based on polycaprolactone. By selective hydrolysis of urethane blocks in the presence of acid, it was possible to obtain the insoluble polyimide film for the first time. It was shown that the combination of thermal and acid treatment allowed almost complete removal of urethane blocks from the initial copolymer chains. IR spectroscopy, TGA, DSC and DMA methods were used to study the evaluation of the structure and properties of polymeric material as a result of thermal oxidation and hydrolysis by acid. It was shown that the polymeric films obtained by controlled decomposition were not soluble in aprotic solvent, such as dimethylformamide, n-methylpyrrolidone and dimethyl sulfoxide, and showed very close similarity to the homopolymer consisting of the same imide monomer, poly-(4,4′oxydiphenylene)pyromellitimide, confirming the feasibility of the proposed concept and its perspectives for fabrication of organic solvent-resistant membranes.

An ultrapermeable thin film composite membrane supported by “green” nanofibrous polyimide substrate for polar aprotic organic solvent recovery

The preparation of polymeric-based thin film composite (TFC) membrane with high permeance and superior solvent resistance in organic solvent nanofiltration (OSN) applications always involves the consumption of toxic chemicals or high energy, which does not meet the requirements of green chemistry. In this work, intrinsic insoluble polyimide (PI) nanofiber substrates were obtained by a two-step method including electrospinning of poly (amic acid) synthesized by polycondensation reaction between various monomers and subsequent thermal imidization, and the optimized one with low thermal imidization temperature was employed as substrate for TFC membrane in strong polar aprotic solvents recovery, therefore achieving the green process. The effects of different dianhydride and diamine monomers and different thermal imidization temperatures on the solvent resistance and microscopic morphology of nanofiber substrates are also studied. The optimized monomers in this work contribute to a low-temperature imidization of PI nanofiber substrate. The solvent permeance of corresponding TFC OSN membrane with the insoluble PI nanofiber substrate reaches up to 11.2 L m −2 h −1 bar −1 with 99.7% rejection in rose bengal/DMF system, and good long-term stability. This work provides potential guidelines for developing next-generation OSN membranes under a green process. • Insoluble polyimide (PI) nanofibrous substrate was prepared facilely with low-temperature thermal imidization. • A green modification without toxic chemical solvent involved is applied. • PI nanofibrous substrate can withstand strong polar aprotic solvents for more than three months. • The high porosity and interconnected pores endow substrate superior solvent permeance. • TFC membrane exhibits outstanding OSN performance and long-term stability.

Improved toughness of phthalonitrile composites through synergistic toughening methods

Brittleness has long been a trouble for the application of phthalonitrile polymers in high temperature structural composites. In this work, crosslinkable poly(aryl ether nitrile) and insoluble polyimide particles were first selected as binary toughening modifiers for synergistic toughening of phthalonitrile composites, respectively. Various mechanical measurements and thermal tests were adopted to systematically evaluate the toughening effects as well as heat resistance. The optimized composites exhibited GIC of 659.7 J/m2 and GIIC of 907.1 J/m2, while ILSS increased to 78.6 MPa. More importantly, its glass transition temperature was 449 °C, which was only slightly lower than the blank contrast. Later, the mechanism for this synergistic toughening was proposed and discussed.

Highly solvent-durable thin-film molecular sieve membranes with insoluble polyimide nanofibrous substrate

Permselective thin-film composite membranes are gaining a significant role in solvent-based molecular sieving applications. Nevertheless, the lack of desirable substrate materials, which combines high flux, solvent resistance as well as a straightforward fabrication process, is still the biggest bottleneck for large-scale commercial implementation. For the first time, we propose to fabricate an insoluble polyimide nanofibrous substrate by a sequential strategy involving electrospinning polyamic acid followed by a thermal imidization. The water-absent electrospinning process leads to 1-fold enhanced mechanical strength and higher solvent-resistance of substrate compared to the conventional phase inversion process. The resultant thin-film nanofibrous composite (TFNC) membranes exhibit exceptional potential for nanofiltration by showing high permeability, rejection, and stability in water as well as polar aprotic solvents such as dimethylformamide, dimethyl sulfoxide, and tetrahydrofuran compared to state-of-art membranes. The strategy of using electrospun insoluble polyimide as the substrate establishes a scalable approach to design high-performance TFNC membranes for a wide range of challenging molecular sieving applications.

Asymmetric hollow-fiber filtration membranes based on insoluble polyimide (R-BAPB): Influence of coagulation bath on porous structure

The insoluble polyimides are the most promising group of polymer materials for fabrication of solvent stable filtration membranes suitable for operation at elevated temperatures. In order to synthesize asymmetric membranes from insoluble polyimide, it is proposed to fabricate the membranes from a pre-polymer solution (polyamide acid – PAA) by non-solvent induced phase separation method followed by imidization to form non-soluble porous polyimide membrane. The thermoplastic crystallizable polyimide R-BAPB, which is resistant to a number of known organic solvents, was chosen as a membrane material. For the first time, hollow fiber membranes based on imidized PAA (R-BAPB) with a controlled distribution of pores on the inner side of the hollow fiber were formed. It has been established that the use of “hard” non-solvents, such as water or aqueous-organic solutions, is preferable for the formation of a porous structure in the membranes based on PAA (R-BAPB). Synthesized PAA membranes were used to prepare porous membranes based on the thermoplastic polyimide R-BAPB by thermal imidization. Imidization process was confirmed by an increase in the glass transition temperature of the material to 220 °C (corresponds to the glass transition temperature of polyimide (R-BAPB)) and is accompanied by a significant increase in its elastic modulus. The results of the measurements of the transport properties of polyimide membranes for gases and liquids indicate that microfiltration transport pores are present in the membranes.

Preparation of Thermally Imidized Polyimide Nanofiltration Membranes with Macrovoid-Free Structures

Insoluble polyimides (PIs) are ideal materials for organic nanofiltration membranes. However, the membranes have to be prepared using soluble polyamic acid and then converted to PIs via chemical or...

Ultralong Life Organic Sodium Ion Batteries Using a Polyimide/Multiwalled Carbon Nanotubes Nanocomposite and Gel Polymer Electrolyte

Organic cathode materials are of great interest for application in batteries due to their abundant availability and environmental compatibility. An approach to make long chain molecules of these organic materials in order to overcome the problem of dissolution in a liquid electrolyte (LE) and incorporate a highly conducting material to enhance the poor electric conductivity of these materials would be of great research interest. In this work, a novel polyimide (PI)/multiwalled carbon nanotube (MWCNT) nanocomposite is prepared as the cathode material for organic Na-ion batteries (NIBs), via a two-step imidization reaction using perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) and diaminopropane (DAP) to form an insoluble PI. The MWCNT in the composite serves as the conductive channel to maximize the utilization of the active material in the electrode. Furthermore, a three-dimensional fiber network is prepared from an electrospun polyacrylonitrile nanofibrous membrane and used as a gel polymer electrol...

Film Polymerization − A New Route to the Synthesis of Insoluble Polyimides Containing Functional Nickel(II) Schiff Base Units in the Main Chain

AbstractThe synthesis and characterization of a new, amino‐derivatized functional bis(salicylaldiminato)NiII complex is reported. It is a useful and reactive precursor in the synthesis of polyimide thermosets. Thus, the first synthesis of a polyimide containing a nonlinear optical NiII Schiff base complex in the main chain is achieved by thermally controlled film polymerization. Polymerization was monitored on silicon substrates by FT‐IR spectroscopy. The polymer film possesses characteristics analogous to those of the insoluble polymer obtained by polymerization in solution, as evidenced by FT‐IR spectroscopy and TGA analysis. The present approach might represent a general strategy for achieving thin films of insoluble, functional polymers. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Organo-soluble polyimide (TBAPP–OPDA)/clay nanocomposite materials with advanced anticorrosive properties prepared from solution dispersion technique

A series of organic soluble polymer–clay nanocomposite (PCN) materials that consist of organic soluble polyimide (SPI) and layered montmorillonite (MMT) clay are successfully prepared by the solution dispersion technique. The as-synthesized PCN materials are characterized by infrared spectroscopy, wide-angle powder X-ray diffraction, transmission electron microscopy and scanning electron microscopy.Polymer–clay nanocomposite materials, in the form of coating, incorporating with low clay loading on cold-rolled steel (CRS) are found much superior in anticorrosion over those of bulk SPI on the basis of a series of electrochemical measurements of corrosion potential, polarization resistance and corrosion current in 5 wt% aqueous NaCl electrolyte. Effects of the material composition on the O2/H2O molecular permeability, optical clarity and thermal stability of SPI along with PCN materials, in the form of both membrane and fine powder, are also studied and compared to insoluble polyimide system prepared from the thermal imidization by molecular permeability analysis, UV–vis transmission spectra, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively.

Characterization of an insoluble polyimide oligomer by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

In the past two years, papers have appeared in the literature which demonstrate that matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectra can be obtained from matrix-analyte preparations which have been produced by grinding the two materials together until a powder of small particle size is obtained. In the present study that methodology was modified and applied to an insoluble polyimide oligomer, poly(4,4'-oxydiphenylenepyromellitimide) (POPM). Two matrix materials were employed in this analysis, 1,8 dihydroxyanthrone (dithranol) and 3-aminoquinoline, with and without an additional cationizing agent. The spectra obtained by this method are shown to be sensitive to the matrix employed in the analysis as well as the quantity of cationizing agent combined with the matrix.

Preparation and characterization of organosoluble copolyimides based on a pair of commercial aromatic dianhydride and one aromatic diamine, 1,2-bis(4-aminophenoxy)-4- tert -butylbenzene, series

A series of copolyimides with high molecular weights, excellent mechanical properties, heat-resistant properties, and good solubilities in organic solvents were synthesized from six kinds of commercial dianhydrides and 1,2-bis(4-aminophenoxy)-4-tert-butylbenzene. Monomers for synthesizing insoluble polyimides and monomers for synthesizing soluble polyimides were used to synthesize semialternating copolyimides with arbitrary solubilities. Fifteen kinds of soluble copolyimides were synthesized through chemical or thermal cyclodehydration. These copolyimides were found to be easily soluble as well as able to be processed by casting from solutions such as N-methyl-2- pyrrolidone, N,N-dimethylacetamide, dimethylformamide, dimethyl sulfoxide, m-cresol, and tetrahydrofuran. The easily dissolved characteristics of this series of copolyimides stemmed from the tert-butyl group, the ortho-linked aromatic unit, and the ether group within 4-tert-butylbenzene. Besides, when the dianhydride molecules used contained organosoluble groups and were mixed at varying molar ratios, the solubilities in organic solvents could be greatly enhanced. The copolyimides could improve the processability of polymers, while maintaining or increasing their excellent mechanical properties and heat-resistant properties.

Bipolar Transport in Aromatic Polyimides

Electron and hole drift mobilities were measured by the time-of-flight technique in films of aromatic polyimides based on 9,10-bis(p-aminophenyl)anthracene or 9,10-bis(phenylthio)anthracene and a series of diimide fragments. The electric field and temperature dependences of the mobilities were detected. In amorphous films of the soluble polyimide, the drift mobility was found to reach the value of 10−4 cm2 V−1s−1 at 5.5 × 105 V cm−1. In the insoluble polyimides films, the mobility was lower by one or two orders of magnitude. This is attributed to the presence of cavities in the films of the insoluble polyimides.

A comparative study of insoluble and soluble polyimide thin films

Physical properties of thin films of soluble and insoluble aromatic polyimides were compared by d.s.c., u.v.-visible and fluorescence spectroscopy, and prism coupler technique. D.s.c. results showed that the thermal properties of insoluble polyimides are superior to those of soluble ones, owing to the specific molecular interactions of insoluble polyimides, revealed by fluorescence spectroscopy. However, the specific molecular interactions sacrifice the transparency in their thin films, shown by u.v.-visible transmission spectra. Negative birefringence of thin films, not only for soluble polimides but also for polyamic acids of insoluble polyimides, was confirmed by prism coupler, while thin films of insoluble polyimides thermally imidized lack high levels of negative birefringence. It is regarded that thin films of insoluble polyimides thermally imidized are likely to be isotropic because of molecular relaxation above their glass transition temperatures ( T g in the course of thermal imidization, according to Flory's principle. On the contrary, thin films of insoluble polyimide chemically imidized keep the same levels of negative birefringence as those of the relevant polyamic acid thin films. Judging from the opposite cases, it is recognized that molecular relaxation above T g weakens the optical anisotropy of polyimide thin films.

Charge carrier transport in polyimides based on 9,10-bis(p-aminophenyl)anthracene

Transient currents were measured by the time-of-flight technique in films of aromatic polyimides based on 9,10-bis(p-aminophenyl)anthracene and a series of diimide fragments. The electric field and temperature dependences of the hole and electron drift mobilities were detected. In amorphous films of the soluble polyimide with a phthalide group in the diimide fragment, the drift mobility was found to reach the value of 10-4cm2V-1s-1 at 5·5×105Vcm-1 and 291K. In the insoluble polyimide films including the crystalline phase, the mobility was lower by one or two orders of magnitude. This is attributed to the presence of cavities in the films of the insoluble polyimides. The applicability of known theoretical models describing temperature and electric field dependences of the drift mobility is discussed. © 1998 Society of Chemical Industry

Gas transport properties and structural order of poly(4,4′-oxydiphenylene piromelliteimide) in composite membranes

Abstract Specific physico-chemical properties of aromatic polyimides determine their high selectivity in gas separation and relatively low gas permeability. Gas transport properties of insoluble polyimides may be improved in the process of membrane formation. A two-stage process was used for making composite membranes comprised of poly(4,4′-oxydiphenylene pyromelliteimide) (PI) and poly(2,6-dimethyl-1,4-phenylene oxide) (PPO). In the first stage the polyamic acid (PAA)/PPO membrane was formed by casting a 5% PAA solution on the surface of the PPO support. The second stage of solid-phase imidization led to obtaining a PI/PPO membrane. Catalytic, chemical and thermal methods of imidization with heating to 150°C were compared. It was established that the catalytic method is the simplest and most reliable in the preparation of membranes with the best gas transport properties. The interaction between the PAA prepolymer and benzimideazole (BI) catalyst was studied. The formation of a PAA:BI complex is favourable to imide ring formation at lower temperature. The PI/PPO membrane was analysed on the basis of the resistance model. It was shown that resistance to gas flow through the PI/PPO composite membrane is determined principally by the zone of homogeneous film in the PI top layer. The analytical data on the membrane structure was verified by electron microscopy data. It was concluded that low-temperature solid-phase catalytic imidization is a promising method for making composite membranes based on insoluble polyimides.

New screen printable polyimide for IC devices

To develop a new screen-printable polyimide paste, structures, properties, and the ratios of three major paste components (filler, binder, and solvent) were studied and a new film-forming strategy was established. This strategy comprises a new type of polyimide particle filler which can be dissolved in the binder and the solvent under the curing condition. Using this strategy, the new screen-printable polyimide paste was developed. This paste produces a uniform film with better mechanical properties than conventional polyimide paste which is comprised of an insoluble polyimide particle filler. The effect of the solubility parameter of the solvent on mask swelling and moisture resistance was also examined. It was found that a lactone with a solubility parameter value of 18-20 (MJ/M/sup 3/)/sup 1/2/ is suitable as a paste solvent and the lifetime of the stencil is extended over that of the conventional paste.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

4,4′‐Isophthaloyidiphthalic anhydride polyimides

AbstractA series of polyimides based on 4.,4′‐isophthaloyldiphthalic anhydride (IDPA) was prepared and characterized by inherent viscosity, differential scanning calorimetry (DSC), solubility, wide‐angle X‐ray scattering (WAXS), and isothermal thermogravimetric analysis (ITGA). Film forming, tough, insoluble polyimides were obtained with most of the 11 diamines used for evaluation. Two materials were semicrystalline. Several compositions showed excellent thermooxidative stability by ITGA at 300 and 350°C in air, as compared to Kapton‐H (Du Pont) film. The IDPA‐m‐phenylenediamine (m‐PDA) composition, for example, gave a flexible, amorphous film having a Tg of 259°C (identical with LARC‐TPI) and insoluble in a wide range of solvents. It is based on a potentially low‐cost dianhydride (IDPA) and, unlike LARC‐TPI, a low‐cost, domestically available diamine which gives a negative Ames test.

Flexibility of aromatic polyimides and polyamidoacids

A theoretical study is carried out on the flexibility of aromatic polyamidoacids and polyimides containing planar cycles connected by different types of joints. It is shown that such polymer chains may be considered as a sequence of linear links joined at some angles with free rotation about the links. An expression for the mean square end-to-end distance for some types of these chains is given. An experimental investigation of the flexibility of some polyamidoacids obtained by polycondensation is also performed. The intrinsic viscosity is measured in θ-solvent. The molecular weight is determined by light scattering. The agreement between experimental and theoretical values of ( h 0 2/ M) 1,2 for polyaminoacids is satisfactory thus justifying the use of the suggested theoretical approach for study of the flexibility of insoluble polyimides.

Polyaryleneimides of meso‐ and dl‐ 1,2,3,4‐butanetetracarboxylic acid dianhydrides

AbstractHigh molecular weight polyarylene amic acids have been prepared by reacting aromatic diamines with equimolar amounts of either meso‐or dl‐1,2,3,4‐butanetetracarboxylic acid dianhydride (TCBA) in organic polar solvents. Heat converted these soluble precursors to insoluble polyimides having good high‐temperature physical properties.